We wish to describe an efficient and rapid synthesis of isoxazolines by the reaction of substituted pyrazol-5-one were condensed with hydroxylamine hydrochloride in presence of clay (pH =12.5) and PEG-400 as a green reaction media. Herein, we report the conventional condensation method of substituted pyrazol-5-one with hydroxylamine hydrochloride in PEG-400 as reaction solvent at mild reaction condition. Structures of the synthesized compounds were confirmed by the spectral analysis. Furthermore, all the synthesized compounds were evaluated for their antimicrobial screening against several pathogenic representatives, these newly synthesized compounds were screened for their antimicrobial activity against bacterial strain Escherichia coli (MTCC-443), Bacillus subtilis (MTCC-441), Staphylococcus aureus (MTCC-96) and Salmonella typhi. (MTCC-98). The antifungal activity was evaluated against Aspergillus niger (MTCC-1781), Aspergillus flavus (MTCC-3008), Candida albicans (MTCC-227) and Penicillium chrysogenum (MTCC-160).The result revealed that most of the compounds showed good to moderate Antimicrobial screening. The major advantages of this protocol are it gives excellent yields of products, work up procedure and isolation is easier, Procedure is green and environmentally benign, shorter reaction times.